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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.imageio.spi;

import java.io.File;
import java.io.IOException;
import javax.imageio.stream.ImageOutputStream;

/**
 * The service provider interface (SPI) for
 * <code>ImageOutputStream</code>s.  For more information on service
 * provider interfaces, see the class comment for the
 * <code>IIORegistry</code> class.
 *
 * <p> This interface allows arbitrary objects to be "wrapped" by
 * instances of <code>ImageOutputStream</code>.  For example, a
 * particular <code>ImageOutputStreamSpi</code> might allow a generic
 * <code>OutputStream</code> to be used as a destination; another
 * might output to a <code>File</code> or to a device such as a serial
 * port.
 *
 * <p> By treating the creation of <code>ImageOutputStream</code>s as
 * a pluggable service, it becomes possible to handle future output
 * destinations without changing the API.  Also, high-performance
 * implementations of <code>ImageOutputStream</code> (for example,
 * native implementations for a particular platform) can be installed
 * and used transparently by applications.
 *
 * @see IIORegistry
 * @see javax.imageio.stream.ImageOutputStream
 */
public abstract class ImageOutputStreamSpi extends IIOServiceProvider {

  /**
   * A <code>Class</code> object indicating the legal object type
   * for use by the <code>createInputStreamInstance</code> method.
   */
  protected Class<?> outputClass;

  /**
   * Constructs a blank <code>ImageOutputStreamSpi</code>.  It is up
   * to the subclass to initialize instance variables and/or
   * override method implementations in order to provide working
   * versions of all methods.
   */
  protected ImageOutputStreamSpi() {
  }

  /**
   * Constructs an <code>ImageOutputStreamSpi</code> with a given
   * set of values.
   *
   * @param vendorName the vendor name.
   * @param version a version identifier.
   * @param outputClass a <code>Class</code> object indicating the legal object type for use by the
   * <code>createOutputStreamInstance</code> method.
   * @throws IllegalArgumentException if <code>vendorName</code> is <code>null</code>.
   * @throws IllegalArgumentException if <code>version</code> is <code>null</code>.
   */
  public ImageOutputStreamSpi(String vendorName,
      String version,
      Class<?> outputClass) {
    super(vendorName, version);
    this.outputClass = outputClass;
  }

  /**
   * Returns a <code>Class</code> object representing the class or
   * interface type that must be implemented by an output
   * destination in order to be "wrapped" in an
   * <code>ImageOutputStream</code> via the
   * <code>createOutputStreamInstance</code> method.
   *
   * <p> Typical return values might include
   * <code>OutputStream.class</code> or <code>File.class</code>, but
   * any class may be used.
   *
   * @return a <code>Class</code> variable.
   * @see #createOutputStreamInstance(Object, boolean, File)
   */
  public Class<?> getOutputClass() {
    return outputClass;
  }

  /**
   * Returns <code>true</code> if the <code>ImageOutputStream</code>
   * implementation associated with this service provider can
   * optionally make use of a cache <code>File</code> for improved
   * performance and/or memory footrprint.  If <code>false</code>,
   * the value of the <code>cacheFile</code> argument to
   * <code>createOutputStreamInstance</code> will be ignored.
   *
   * <p> The default implementation returns <code>false</code>.
   *
   * @return <code>true</code> if a cache file can be used by the output streams created by this
   * service provider.
   */
  public boolean canUseCacheFile() {
    return false;
  }

  /**
   * Returns <code>true</code> if the <code>ImageOutputStream</code>
   * implementation associated with this service provider requires
   * the use of a cache <code>File</code>.
   *
   * <p> The default implementation returns <code>false</code>.
   *
   * @return <code>true</code> if a cache file is needed by the output streams created by this
   * service provider.
   */
  public boolean needsCacheFile() {
    return false;
  }

  /**
   * Returns an instance of the <code>ImageOutputStream</code>
   * implementation associated with this service provider.  If the
   * use of a cache file is optional, the <code>useCache</code>
   * parameter will be consulted.  Where a cache is required, or
   * not applicable, the value of <code>useCache</code> will be ignored.
   *
   * @param output an object of the class type returned by <code>getOutputClass</code>.
   * @param useCache a <code>boolean</code> indicating whether a cache file should be used, in cases
   * where it is optional.
   * @param cacheDir a <code>File</code> indicating where the cache file should be created, or
   * <code>null</code> to use the system directory.
   * @return an <code>ImageOutputStream</code> instance.
   * @throws IllegalArgumentException if <code>output</code> is not an instance of the correct class
   * or is <code>null</code>.
   * @throws IllegalArgumentException if a cache file is needed, but <code>cacheDir</code> is
   * non-<code>null</code> and is not a directory.
   * @throws IOException if a cache file is needed but cannot be created.
   * @see #getOutputClass
   */
  public abstract ImageOutputStream createOutputStreamInstance(Object output,
      boolean useCache,
      File cacheDir)
      throws IOException;

  /**
   * Returns an instance of the <code>ImageOutputStream</code>
   * implementation associated with this service provider.  A cache
   * file will be created in the system-dependent default
   * temporary-file directory, if needed.
   *
   * @param output an object of the class type returned by <code>getOutputClass</code>.
   * @return an <code>ImageOutputStream</code> instance.
   * @throws IllegalArgumentException if <code>output</code> is not an instance of the correct class
   * or is <code>null</code>.
   * @throws IOException if a cache file is needed but cannot be created.
   * @see #getOutputClass()
   */
  public ImageOutputStream createOutputStreamInstance(Object output)
      throws IOException {
    return createOutputStreamInstance(output, true, null);
  }
}
